Subtract.
Answer: There are many ways to solve this problem. Let's see two ways we can solve it. Place Value We can think in terms of hundredths: $\begin{aligned} &\phantom{=}65.79 - 42.58\\\\ &=6{,}579\text{ hundredths} - 4{,}258\text{ hundredths}\\\\ &=2{,}321\text{ hundredths}\\\\ &=23.21 \end{aligned}$ Place value table Let's line up the numbers by their decimal places. Tens Ones $.$ Tenths Hundredths ${6}$ ${5}$ $.$ ${7}$ $9$ $4$ $2$ $.$ ${5}$ $8$ Now, let's subtract each place value column. Tens Ones $.$ Tenths Hundredths ${6}$ ${5}$ $.$ ${7}$ ${9}$ $-$ $4$ $2$ $.$ ${5}$ $8$ $\underline{~~~~}$ $\underline{~~~~}$ $\underline{~~~~}$ $\underline{~~~~}$ $2$ $3$ $.$ $2$ $1$ $23.21 = 65.79 - 42.58$